The present invention relates generally to 4-N-substituted derivatives of fortimicin B, their pharmaceutically acceptable acid addition salts, and a process for producing the same, as well as novel synthetic processes for producing the compounds fortimicin A and fortimicin C.
Fortimicins (A, B and C) are compounds classified as pseudodisaccharides containing 1,4-diaminocyclitol. The physical properties and antibacterial activities of these compounds and processes for production thereof by fermentation are described in U.S. Pat. Nos. 3,931,400, 3,976,768, and 4,048,015, which descriptions are incorporated herein.
The planar structural formulae of the known fortimicins are shown in the above-mentioned United States specifications. As a result of further studies, it has been found that the structural formulae of fortimicin B, fortimicin A and fortimicin C are given by the following formulae: ##STR1## Structures of fortimicins A, B and C are described below: (1) Fortimicin B
Results of mass spectrum of fortimicin B are given below:
m/e 349(M.sup.+ +1), 348(M.sup.+), 331, 313, 305, 235, 217, 207, 143, 126. PA0 (2) Fortimicin A PA0 (3) Fortimicin C
It is presumed from the results of the mass spectrum that fortimicin B has the following partial structural formula containing purpurosamine B. ##STR2##
The results from the analysis of PMR spectrum and CMR spectrum of fortimicin B in deuterium oxide are given below:
______________________________________ PMR .delta.(ppm) Internal standard DSS ______________________________________ H--1' 5.03 H--1 2.96 H--2' .about.2.9 H--2 3.68 CH.sub.2 --3',4' 1.2-1.9 H--3 3.62 H--5' .about.3.6 H--4 3.06 H--6' 2.80 H--5 3.96 CH.sub.3 --6' 1.00 H--6 3.42 OCH.sub.3 3.42 NCH.sub.3 2.36 J.sub.1',2' 3.8 J.sub.1',2 9.5 J.sub.5',6' 7 J.sub.2',3 .about.3 J.sub.3',4 3 J.sub.4',5 4.5 J.sub.5',6 9.5 J.sub.1',6 9.5 ______________________________________ CMR .delta.(ppm) Internal standard Dioxane (67.4 ppm) ______________________________________ C--1' 102.4 C--1 53.8 2' 50.6 2 71.1 3' 27.1 3 79.9 4' 27.4 4 60.8 5' 75.1 5 71.1 6' 50.4 6 84.1 6' -CH.sub.3 18.7 OCH.sub.3 59.3 NCH.sub.3 36.0 ______________________________________
From these data of PMR and CMR, and spectrophotometric data of copper complexes of fortimicin B, diethylthioacetal derivative of purpurosamine B portion, and methyl glycoside derivative prepared according to the conventional processes, the absolute structure of fortimicin B has been determined to be: ##STR3## Other physical data of fortimicin B are: m.p. 101.degree.-103.degree. C.
[.alpha.].sub.D.sup.23.degree. =+30.3.degree. (c=1.0, water). PA1 Elemental analysis as C.sub.15 H.sub.32 N.sub.4 O.sub.5.H.sub.2 O: Calculated: C, 49.15; H, 8.80; N, 15.29. Found: C, 49.36; H, 8.77; N, 15.38. PA1 Mass spectrum: m/e 406(M.sup.+ +1), 405(M.sup.+), 388, 370, 362, 292, 274, 263, 246, 143, 126. PA1 PMR (deuterium oxide: .delta.(ppm), 1.06(3H,d), 1.2-1.9(4H,m), .about.2.8(1H,br), 2.86(1H,m), 3.05(3H,s), 3.44(3H,s), .about.3.5(2H,br), 3.52(2H,s), 3.88(1H,q), 4.08(1H,q), 4.16(1H,t), 4.36(1H,t), 4.84(1H,d), 4.95(1H,q). PA1 CMR (deuterium oxide): .delta.(ppm), 18.7, 27.1, 27.3, 32.3, 41.6, 50.2, 50.5, 52.5, 55.0, 56.4, 71.1, 73.0, 73.6, 75.1, 78.4, 100.1, 169.5. PA1 m.p.: above 200.degree. C.(dec.). PA1 [.alpha.].sub.D.sup.25.degree. =+26.0.degree. (c=0.2, water). PA1 Elementary analysis as C.sub.17 H.sub.35 N.sub.5 O.sub.6 : Calculated: C, 50.35; H, 8.70; N, 17.27. Found: C, 50.23; H, 8.67; N, 17.49. PA1 Mass spectrum**: m/e 406, 387, 375, 325, 292, 274, 264, 246, 235, 228, 217, 207, 200, 143 PA1 PMR (deuterium oxide): .delta.(ppm), 1.08(3H,d), 1.2-1.9(4H,m), .about.2.8(1H,br), 2.85(1H,m), 3.10(3H,s), 3.43(3H,s), .about.3.5(2H,br), 3.87(1H,q), 4.00 and 4.04 (jointly 2H, individually s), 4.07(1H,q), 4.18(1H,t), 4.38(2H,t), 4.84(1H,d), 4.92(1H,q). PA1 CMR (deuterium oxide): .delta.(ppm), 17.5, 26.3, 27.5, 32.5, 44.1, 50.0, 51.1, 52.7, 55.5, 56.4, 71.0, 72.7, 73.1, 73.4, 77.9, 99.1, 161.7, 172.7 FNT *Mass spectrum where M.sup.+ is liable to appear. FNT **M.sup.+ fails to appear in ordinary mass spectrum (EI mass spectrum) PA1 m.p.: 153.degree.-157.degree. C. (dec.) PA1 [.alpha.].sub.D =+84.3.degree. (c=0.1, water) PA1 Elementary analysis as C.sub.18 H.sub.36 N.sub.6 O.sub.7.2H.sub.2 O: Calculated: C, 45.00; H, 8.33; N, 17.50: Found: C, 44.84; H, 8.19; N, 17.36. PA1 A: isopropanol-28% aqua ammonia-chloroform (2:1:1 by volume) PA1 B: methanol: chloroform (5.95 by volume) PA1 C: methanol: chloroform (1:9 by volume) PA1 S.A.: Staphylococcus aureus KY4279 ATCC6538P PA1 B.S.: Bacillus subtilis KY 4273 PA1 E.C.: Eschericia coli KY4271 ATCC26 PA1 P.V.: Proteus vulgaris KY4277 ATCC6897 PA1 S.S.: Shigella sonnei KY4281 ATCC9290 PA1 S.T.: Salmonella typhosa KY4278 ATCC9992 PA1 K.P.: Klebsiella pneumoniae KY4275 ATCC10031
Other physical data of fortimicin A are:
From the foregoing data, and the fact that hydrolysis of fortimicin A produces fortimicin B and glycine, the structure of fortimicin A has been confirmed to be 4-N-glycylfortimicin B (Ia).
Field desorption (FD) mass spectrum*: m/e 449(M.sup.+ +1).
Other physical data of fortimicin C are given below:
From the foregoing data, and a fact that hydrolysis of fortimicin C produces fortimicin B and hydantoic acid, the structure of fortimicin C has been found to be 4-N-hydantoyl fortimicin B (IIb) (fortimicins A and C have been synthetically derived from fortimicin B as given in Examples, and then the structures have been confirmed).
Fortimicins (A, B and C) all have antibacterial activity, but the antibacterial activity of B is not as good as the other factors; and A and C are slightly unstable under strongly alkaline conditions. Therefore, compounds having more distinguished properties are in demand.
As a result of various studies, the present inventors have found that certain 4-N-substituted derivatives of fortimicin B have enhanced antibacterial activity and good stability even under strongly alkaline conditions. Furthermore, the 4-N-alkyl-fortimicin B derivatives can be used as starting materials for further modified derivatives, i.e. introduction of other group(s) to the amino or hydroxy group(s) thereof.